2026 ICD-10-CM Diagnosis Code M31.4Aortic arch syndrome [Takayasu]
ICD-10-CM Codes›M00–M99›M30-M36›M31
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 93
- Chronic Condition
M31.4 is a billable ICD-10-CM diagnosis code for aortic arch syndrome [Takayasu]. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 545 through 547. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 74 closely related codes. Coders also document this condition as cerebrovascular abnormality due to Takayasu disease. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Systemic lupus erythematosus and connective tissue disorders and Vasculitis.
For Medicare Advantage risk adjustment, M31.4 maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders) under the V28 model, adding a risk factor of about 0.617 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M31.4 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Cerebrovascular abnormality due to Takayasu disease
- Primary systemic arteritis
- Takayasu's disease
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
aortic arch M31.4
brachiocephalic M31.4
Disease, diseased See Also: Syndrome;
pulseless M31.4
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Aortic Arch Syndrome
a syndrome resulting from structural defects of the arteries that arise from the aortic arch. signs and symptoms include weakness, dizziness, arm numbness, blurred vision and transient ischemic attacks.Aortic Arch Syndrome due to Takayasu Arteritis|Aortic arch syndrome [Takayasu]
aortic arch syndrome caused by takayasu arteritis.
Patient EducationClinical
Vasculitis
Vasculitis is an inflammation of the blood vessels. It happens when the body's immune system attacks the blood vessel by mistake. It can happen because of an infection, a medicine, or another disease. The cause is often unknown.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M31.4 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M31.4Overview
What is the ICD-10 code for aortic arch syndrome [Takayasu]?
The ICD-10-CM code for aortic arch syndrome [Takayasu] is M31.4 (sometimes written as M314). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M31.4 (Other necrotizing vasculopathies) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report aortic arch syndrome [Takayasu] on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M31.4 group to?
When aortic arch syndrome [Takayasu] is the principal diagnosis on an inpatient stay, it groups to MS-DRG 545, 546, 547, with relative weights from 0.8362 to 2.4817 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M31.4 a CC or MCC?
CMS lists M31.4 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 74 closely related codes in its exclusion list.
What is the ICD-9 equivalent of M31.4?
Under the General Equivalence Mappings, aortic arch syndrome [Takayasu] converts to ICD-9-CM 446.7 (Takayasu's disease). The mapping is a direct match.
What HCC is M31.4?
M31.4 (aortic arch syndrome [Takayasu]) maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders), commonly written as HCC 93, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 40 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 84.
Does M31.4 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M31.4 adds a risk adjustment factor of about 0.617 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.288 to 0.617 depending on the payment segment). HCC 93 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 93 category page.
